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F b- 1954 l. A. WEAVER ETAL BALANCE TESTING APPLIANCE 7 Sheets-Sheet 1 Original Filed July 20, 1945 I N VEN TORS JFQ Q. 1/6306? Cgaefl 5 Feb. 16, 1954 WEAVER ETAL Re. 23,785

BALANCE TESTING APPLIANCE Original Filed July 20, 1945 7 Sheets-Sheet 2 INVENTORS, 95 17 4 Q wea /e7 75 Q Puw g5 Feb. 16, 1954 L WEAVER ETAL Re. 23,785

BALANCE TESTING APPLIANCE Original Filed July 20, 1945 7 Sheets-Sheet I5 [Zia J JQQ J0 76 PLAN I N VEN TORS 75 72 62 Q, Wmuer' agdeflp/wz 5 IN V EN T 0R.5 Fin 0. Weaver l A WEAVER ET AL BALANCE TESTING APPLIANCE Feb. 16, 1954 Original Filed July 20, 1945 BALANCE TESTING APPLIANCE Original Filed July 20, 1945 7 Sheets-Sheet 5 [NVENTORS g m aw INVENTOR5. 17r a/- Mme/er 7 Sheets-Sheet 6 de f/zel .5

Feb. 16, 19 A WEAVER ETAL BALANCE TESTING APPLIANCE Original Filed July 20, 1945 Feb. 16, 195 1. A. WEAVER ETAL BALANCE TESTING APPLIANCE 7 Sheets-Sheet 7 Original Filed July 20, 1945 zjazmg.

Reiuued Feb. 16, 1954 Ira A. Weaver and Clyde H. Phelps, Springfield, 111., assignors, by mesne assignments, to Gisholt Machine Company, Madison, Wis., a corporation of Wisconsin Original No. 2,487,035, dated November 1, 1949, Serial No. 606,050, July 20, 1945. Application for reissue October 30, 1950, Serial No. 192,992

(Cl. iii-66) 27 Claims.

Matter enclosed in heavy brackets appears in the original matter printed in italics indicates the additions made by reissue.

reissue specification;

This invention concerns certain valuable betterments in balance testing machines such as are used to determine the amount and location of unbalance in a suitably supported revolving rotor whereby the latter is tested as to its dynamic equilibrium and the degree of the latter is indicated by suitable means. The invention is useful to analyze the unbalance of similar rotors so that suitable corrective steps may be taken to bring them to dynamic balance.

An object of the invention is to provide an appliance of this kind which is relatively simple in structure, which is reliable in results, which is of comparatively low cost, which is unlikely to become damaged or injured in ordinary service and which is easily operated.

In order to understand the invention, it is well to deal initially with some fundamental elemental balancing principles and that course will be followed.

In the drawings, forming a part of this specification, and to which reference should be had in connection with the succeeding description:

Figures 1 to 23 inclusive present various diagrams;

Figure 24 is a longitudinal section through one of the crystal electric generators;

Figure 25 is a lengthwise section thereof on line 2525 of Figure 24;

Figure 26 shows the electric circuits in which such generators are used;

Figure 27 is a front elevation of the balance testing machine;

Figure 28 is a plan view of the same machine;

Figure 29 is an end elevation of the machine;

Figure 30 is a fragmentary view of a slightly modified machine; and

Figure 31 is a partial end View of the machine of Figure 30.

By reference to these drawings, it will be noted that Figure 1 represents a disc 5| the shaft of which is mounted on two, parallel, horizontal, V bars or rails 52, 52, this disc being in complete balance except that a weight 53 has been attached to the rim thereof, as illustrated, causing the disc to roll on the rails by reason of the fact that the weight seeks its lowermost position, as shown.

As indicated, in Figure 2, another weight 54 of the same value has been attached to the disc in' the same plane and diametrically opposite weight 53 to bring. the disc to complete static balance, thereby removing its tendency to roll.

Figures 3 and 4 portray a cylinder 55, similarly mounted and in complete static balance, as

patent but forms no part of this 2 the two weights 56 and 51 are of equal value and attached to the perfectly balanced cylinder in the same plane though offset longitudinally of the cylinder, but upon rotation the cylinder is not in dynamic balance.

Figures 5 and 6 present the same cylinder and weight combination as in Figures 3 and 4 and upon rotation of such cylinder, if the latter is freely suspended, the two weights will cause the ends of the cylinder to oscillate in opposite directions, and because the centrifugal force of weight 56 in the direction of its arrow is the opposite of that of weight 51 in the direction of its arrow, the cylinder is diametrically unbal-- anced.

However, if weight; 57 be removed and attached to the cylinder at point 50 in the transverse plane of weight 56 complete balance will be obtained.

Figures '7, 8 and 9 illustrate the same cylinder 55 fitted with unbalance weight 56 corrected by weight 51 opposite and in the same plane and an unbalance weight 58 corrected by weight 59 in the same plane, this cylinder, therefore, being in complete balance both statically and dynamically.

Figure 10 represents the same cylinder 55 with transverse correction planes selected at I00 and II, but the unbalance weight BI is not in either correction plane and, therefore, if -the two weights, 62 in correction plane l 00, and 63 in correction plane IUI, whose sum is equal to that of weight 6|, were removed and a weight equal to that of weight 6| were attached 180 degrees around the cylinder from weight El and in either correction plane, static balance would be obtained but dynamic unbalance would be created. With relation to such statically balanced cylinder, weight 62 multiplied by the distance D equals weight 63 multiplied by the distance 0 and consequently the forces are in balance opposite Weight El and the cylinder is in complete balance.

Figures 11, 12, 13, 14 and 15 show the same cylinder as presented in Figure 10 with the weight 6| balanced by the weights I52 and 63 in the two correction planes I00 and WI and with another unbalance weight 64 balanced by two additional weights E5 and 66 also in the two correction planes I00 and i 0|. The two correction weights 62 and 66 in correction plane lull may be replaced by a single weight of resultant value located at position 61 as indicated in Figure 13 and the correction weights 63 and in correction plane l0! may be replaced by a single weight of resultant value located at position 68 in cor- .complete balance can be obtained, such a machine indicating the resultant value of positions 81 and B8 in Figures 13 and 15.

Accordingly, the present invention relates to balance testing machines of the type arranged to indicate the unbalance in predetermined planes of correction.

Balance testing machines in general have been based upon a flexible mounting to support the motor for rotation with freedom to vibrate in at least one plane, usually the horizontal, in order that the oscillation caused by the unbalance may ,be indicated.

Some balance testing machines have been provided with means to pivot the rotor effectively at one selected correction plane in order to indicate unbalance in another selected plane of correction whereby the unbalanced forces in the plane of the pivot are directed to the pivot and are without effect at another correction plane, but, as the pivot is a stationary part of the frame or mounting. undesirable vibrations are transmitted to the frame causing unreliable indications, as the indicating means are a part of the stationary mounting or frame structure.

Another type of balance testing machine employing a similar flexible mounting means but without the use of a fixed pivot, uses a complex mathematical electrical net-work designed to receive electrical impulses from two generators, operable from each bearing. The two electrical impulses are fed to the complicated electrical net-work which is intended to so combine the impulses received as to give a result in proportion to the unbalance in one correction plane. These generator indicator devices are operable from the motion at the bearings, but are mounted on the frame structure and are, accordingly, subject to objectionable vibrations which may cause inaccurate indications.

Other types of balance testing machines are founded upon a mounting similar to the above, but employing mechanical systems designed to counterbalance the vibration caused by unbalance through counterbalancing mass systems variable in value and angular relation.

The present invention involves the use of freely suspended bearing supports for the rotor arranged so that the rotor may vibrate or oscillate unrestrictedly in the horizontal plane, these bearing supports being arranged for attachment thereto of relatively small, variable mass systems designed to take up vibration similar to that of the rotor, but adjustable to respond to vibrations caused by unbalance in one correction plane of the rotor without effect of unbalance in another plane. The comparatively small variable mass system is a part of the rotor and bearing support and all are free to move as a unit in space and it, therefore, comprises a pendulum suspended seismic mass substantially free from floor or building vibrations.

The variable mass system may be adjusted to respond to the unbalance in any selected plane of correction, and, therefore, one such system may be employed to respond to each or several 4 chosen planes of correction by adjustment of the variable mass system for each plane selected.

For convenience, however, one variable mass system is, or more variable mass systems are, attached to each bearing-support and each adju'ste for response to the unbalance in one selected plane of correction whereby each such system is independent of the others.

An outstanding important object of the invention is the provision of mechanical physical means to permit the accurate.indication of the position and value of unbalance in one correction-plane without effect from unbalance in another plane.

Another aim of the invention is to supply a system with which the testing may be accomplished over a wide speed range in order that rotors may be tested as to balance at a speed at which they normally run in service.

The basis of this invention involves the application of inertia forces set up in the rotor by reason of the unbalance in the planes selected for correction.

In Figure 16 a rotor II is shown with bearings at 12 and 13 with one correction plane selected at 15 in which unbalance 16 has been attached, the rotor otherwise being in perfect balance and suspended on long, thin wires 11, attached to the bearings so that upon rotation, due to the unbalance 18, the rotor will vibrate or oscillate in the horizontal plane through which it has complete freedom of movement.

The same rotor, in a different angular position. is presented in plan view in Figure 17 with the unbalance 16 in the correction plane I5, the horizontal movement of the geometrical center line of the rotor caused by the unbalance 16, being indicated at 18, and because of the mass distribution or inertia quality of the rotor, the unbalance 'IG causes such geometrical center line to move in the direction of and to the position 8| at the left hand end and in the direction of and to the position 82 at the right hand end. Therefore, the, motions at bearing 12 and bearing I3 have a phase difference of 180 degrees, and also at any point of minimum or maximum amplitude of oscillation, the motions of bearings 12 and 13 are in opposite directions or 180 degrees phase difference. However, both bearing 12 and 13 have motion due to the single unbalance present in the correction plane 15. It follows, therefore, that any indication of amplitude of oscillation taken at bearing 13 would include component 83 due to unbalance IS in plane 15, and this component 83 is acting in the opposite direction or 180 degrees from the opposite end of the rotor as at 8 I.

Hence, it is manifest that the component 83 must be eliminated or removed from the indication taken at bearing 13 before a true indication of the unbalance at the correction plane 85 is made.

By reference to Figure 18, the same rotor 1| is again present, excepting that the balance 16 has been removed from correction plane 15 and attached to the rotor in correction plane 85, unbalance 16 now causing oscillation amplitude 86 at the right hand end, and amplitude 81 at the left hand end, and, as before, the motions at bearing 12 and at bearing 13 are in opposite directions or have a phase difference of degrees. Consequently, any indication taken at bearing I2 will include component 88 due to unbalance 1G in correction plane 85. Clearly, then, component 88 must be removed or eliminated from any indication taken at bearing 12 before a correct indicaeaves tion of the unbalance at correction plane I! is made.

Turning now to Figure 19, a rotor 9| with different inertia properties is shown with the unbalance 16 attached thereto in correction plane 85 causing the amplitude of motion 92 at the right hand end and the amplitude 93 at the left hand end, the different inertia quality of this rotor having caused the intersection of the lines of motion to occur at a point to the left of bearing 12. Consequently, the motions of bearings I2 and I3 are in phase with one another as both bearings are moving in the same direction at all times and component 94 at bearing I2 due to the un-- balance in plane 85 is in phase with the motion at bearing I3.

As a result, component 94 must be excluded or banished from any indication taken at I2 before a correct indication of the unbalance at the left hand'correction plane I is made. I

From the foregoing it will be appreciated that the motions at bearings I2 and I3, due to the unbalance in one correction plane, may be either in or out of phase, depending upon the inertia characteristics of the revolving rotor undergoing test.

Turning now to Figure 20, wherein is shown a rotor 99 of still different inertia quality and where the unbalance I6 is attached in the correction plane 85 causing the amplitude of motion 95 at the right hand end but zero motion at bearing 12, the indications taken at point 98 of bearing I2 would not contain any component due to unbalance 16 in plane 85 but would provide reliable indication of unbalance in another correction plane, such as lane 15.

The illustration in Figure 21 is the same as that in Figure 20 except that unbalance I5 has been removed from correction plane 85 and attached to the rotor in correction plane I5 causing the amplitude of motion 91 at the left hand end but zero motion of the bearing I3, so that indications taken at point 98 of bearing I3 would not contain any component due to unbalance IS in plane 15 and would provide reliable indications of unbalance in another correction plane, such as plane 85.

It is, therefore, apparent that the motions at bearings 12 and I3, due to unbalance in one plane, may be in phase or out of phase or one hearing may have zero motion.

The current invention provides a mass system adapted for attachment to the balance-indicating machine in a manner such that it becomes part of the pendulum rotor bearing and hanger system and is, therefore, seismic-mounted and inertia-operated and will vibrate or oscillate in phase with the point of attachment.

Referring to Figure 22, there is shown therein a rotor I02 with unbalance I03 inserted in correction plane 15, this unbalance causing the geometric center line I04 of the rotor to move [have] to position I05 which is the position of maximum amplitude of oscillation in the direction shown.

Points I06 and I01 are 180 out of phase, but points I08 and I09 are exactly in phase, point I09 having attained greater velocity than point I08 in order to reach its maximum amplitude at the same time that point I08 reaches its smaller maximum amplitude.

In Figure 23, the mass H0 and the smaller mass II I, shown as mounted on a common axis I I2 pivoted for rotary movement about the point II3 along the geometric axis or center line II4 of the rotor, having been added to the-structure presented in Figure 22, these two masses III) and I II having individual adiustment on their common axis I I2 along the geometric center line Ill 0! the rotor.

If the mass III having a higher velocity than that of the mass I Ill be adjusted along such com mon axis I I2 toward or away from the heavier mass IIII having a lower velocity, 0. point of adjustment between the two masses may be found where the inertia of the smaller mass of higher velocity will equal the inertia of the larger mass of lower velocity such that zero torque would be applied about pivot H3 during the vibration or oscillation of the rotor and the twomass axis II2 would remain parallel to the geometric center line, prolonged, of the rotor, and therefore the unbalance I03 would have zero torque effect about pivot H3.

It follows that any indicator operable from movement of the two masses about pivot III would provide a zero reading for any unbalance in correction plane I5 but would indicate unbalance in any other transverse plane along the geometric axis of the rotor and that the motion about pivot I I2 would be in phase with, and proportional to, any unbalance in any other transverse plane, except plane I5.

The two masses III! and III adjustably mounted lengthwise on a common axis II2 can be pivotally attached to either bearing 12 or hearing I3 illustrated in the foregoing figures of the drawings and adjusted to provide zero motion about pivot II3 for any unbalance in a selected correction plane whether the motions or vibrations at the bearings are in phase or out of phase, or have zero motion at the bearings.

It is further clear in the case of zero motion at the hearing as in Figure 20 or Figure 21 that one mass only, either III) or III would be required and that one positioned at point 96 of Figure 20, or 98 in Figure 21.

This mass system IIII, III, H2, H3 then provides means to indicate, through the motion about the pivot II3 of Figure 23 the value of the unbalance in a selected plane of correction and its angular position or point of unbalance, without effect from unbalance in any other plane.

In the actual full size balance indicating applianee described in detail below, the rocking or vibration of this two mass system about the axis H3 is employed for operation of a piezoelectric crystal generating element some of the details of which do not of themselves constitute a part of this invention since such an appliance is known.

Referring to Figures 24 and 25, the two weights or masses III! and I I I have screw threaded connections with the straight shaft or rod II2 so that they can be individually adjusted lengthwise thereon, each such weight having a set-screw I I6 for maintaining it in its adjusted position. This shaft II2 extends through a transverse screwthreaded hole in the head II! of a spindle II8, a set-screw II9 holding the part II2 fixedly in its adjusted position in such head and at right angle to the axis of the spindle. Spindle II8 fits inside of a metal member I2I (Fig. 25) in which it is demountably retained by an accessible set-screw I22, equipped with a knurled head I23, extending into a longitudinally divided housing I24.

Member I2l has two, oppositely extended, cylindrical portions I25 and I26 oscillatory respectively in rubber bearings I21 and I28 in the housing.

The two sections of the casing I24 are normal- 1y held together in assembled relation as illustrated by four, hollow rivets I23, I28 by means of which the whole appliance may be readily.-

mounted in proper position, as by screws, not shown, extending through the. rivets.

The inner end of part I26 is provided with a clamp I3I fitting over the corresponding end of the fiat crystal generator I32 consisting of a pair of thin, rectangular crystals of Rochelle salt, tourmaline, quartz, or other comparable minerals Joined together in known manner, the opposite end of the crystals having wires I33 connected thereto and provided with corresponding external terminals I34, I34, such end portion of the crystals being held between fixed rubber or other comparable elastic pads I35, I35, the. construction being such that, when the spindle H8 is turned in either direction from its normal neutral position, the crystals are twisted and strained and by reason of which action they create a minor electric voltage and, as soon as the strain or twist is removed, the crystals automatically return to normal position by reason of the reflex action of the pads I35, I35, the crystals and the spindle being held in this neutral position by the friction of the rubber bearings I21, I28.

The balance testing machine, as presented in Figures 2'7, 28 and 29 includes a suitable base I4I with end standards I43, I43, of the shape depicted in Figure 29 and open at the front at I42 and each supporting a pair of depending wires I44, I44, which at their lower ends support a bearing member I45 rotatably supporting the shaft I46 of the rotor I41 to be tested as to its balance, such rotor being revolved by a belt I48 encircling it and driven by a suitable electric motor I49 on the base I4I.

Each such bearing member I45 has a depending portion II on the lower end of which is mounted one of the two-weight crystal generating members designated as a whole I52 of the type and style presented in Figures 24 and 25, the terminals I34 of which are connected by wires I53 to electric terminals I54 on the standard I43.

A numerically graduated band I55 temporarily encircles and rotates with the rotor I41 and cooperates with the stroboscope lamp I56 and its associated fixed pointer or index I51 of known construction and operation.

Referring to Figure 26, it will be noted that the two terminals I54, I54 of one of the crystal devices I 52 are connected to two electric contacts I6I, I6I and the corresponding terminals I54, I54 of the other crystal generator are connected to the other two terminals I62, I62 of a double-pole double-throw electric switch, characterized as a whole I63, whose terminals are joined to a secend like switch I64 which may connect with a vacuum tube voltmeter I65 or with the stroboscope control amplifier I66 operatively associated with the stroboscope-lamp I56, whereby either crystal generator may be operatively connected to the voltmeter or to the stroboscope lamp.

Preliminary to the testing of the unknown unbalance characteristics of the rotor I41, a like rotor is balanced by trial and error, after which a known unbalance weight is afiixed thereto in the left hand correction plane I15, as illustrated in Figure 27, and, during the rotation of the rotor, the two weights III) and III of the mass system I52 on the right hand bearing member I45 are adjusted longitudinally with respect to one another on their common rod II2 to eliminate all oscillation thereof about the axis I I3 (Fig. 23) of the spindle II8 (Figs. 24 and 25) resulting in zero indication on the associated meter I65 and,

rotor except that in the left hand correction plane I15.

v When the meter gives a zero reading as set forth above, the inertia values of the weights of different amounts are equal and there is, therefore, no tendency to twist the crystals.

When the meter indicates a value of unbalance, it is due to the fact that the two inertia forces of the two masses III) and III are not the same and do not balance one another.

Then this unbalance weight may now be removed from correction plane I15 and applied to the rotor in the right hand correction plane I (Fig. 27) and the mass assembly at the left hand end of the machine adjusted to zero response due to such applied weight and this left hand mass assembly will now respond to unbalance in any plane I85 and the left hand mass assembly will respond proportionately to any unbalance weight attached in the left hand correction plane I15, and, therefore, the indicating device I65 may be calibrated by the use or different amounts 0! unbalance weights to read the response of the mass system to the unbalance in either 01' the two selected planes I15 and I85.

Thereupon, similar or comparable rotors of unknown unbalance properties may be tested without further mass system adjustment, the

volt-meter I65 giving values of unbalance, and the stroboscope lamp and its cooperating graduated band and index giving angular positions of unbalance in each of the two selected planes so that by adding or subtracting proper weight values in these planes exact balance may be readily and quickly procured.

It may be noted that, when either bearing and its associated tester I52 moves in one direction from its normal neutral position and back again to that position, it creates electric-current, by twisting of the crystals, in one direction which increases to a maximum and then back again to zero, and when it moves from its neutral position in the opposite direction and then back again to that position, it develops an opposite current up to maximum and then back to zero value. This device I52 constitutes a form of electric pickup sensitive to oscillatory motion of the rod II 2 with spindle III].

In Figures 30 and 31, a balance testing machine using somewhat diilerent shaped bearing members I61 are shown, one only of these being illustrated. In this case such member. has a forwardly extended, depending arm I68 on the front end of which the crystal generator I52 is mounted rendering the weights I I6 and II I in more favorable position for manual adjustment, but the construction operates precisely as does the other one.

Those acquainted with this art will readily understand that the invention, as defined in the appended claims, is not necessarily limited and restricted to the precise and exact details illustrated and described and that reasonable modifications may be resorted to without departure from the heart and essence of the invention and without the loss or sacrifice of any of its material benefits or advantages.

For example, the point of attachment of the tudinal axis of the mass system is in effect subject to the same angular motion as the geometric longitudinal axis of the rotor, such as the position shown in Figure 23, where the invention is pictured far to the right of the rotor bearing and that of Figure 29 where the horizontal longitudinal axis of screw H2, Figure 24, lies in the plane parallel to the horizontal longitudinal axis of the rotor.

Further the mass H and the mass HI need not be oi unequal weight or size as they may be identical and any desired ratio secured by ad- Justine the screw H2 through the stem nut Ill providing a longer or shorter lever arm about the axis of the member H8 for'either mass.

We claim:

1. Designed to coact with a machine of known type adapted to s pport and to rota e hor zonta ly on its axis a rotor to be tested with free om f r lateral. substantiall hor zontal vibra ion o the rotor due toits unba ance dur ng such rotation a balance testin syste incorporat n the co bination of a piezoelectric cr s al ene ator including a vertical axis pivot havin me ns o erating said generator by turn n of the p vot on ts axis, means mountin said pi ot on said machine in a mann r to subiect such pivot to ai l eral vibration of the rotating rotor. a lon itud nal horizontal su ort fixed to said pivot and e tending on opposite sides of said pivot paral el to the geometric axis of said rotor when such sup ort is in its normal, neutral position, a pair of inertia weights adiustably mounted on said su port on opposite sides of said pivot axis and manually adjustable longitudinally on said support toward and from one another. an electric circuit con-- nected to said piezoelectric crystal generator. and an electric meter usable in said circuit to which the voltage created by said enerator is conducted and by which it is indicated, whereby said inertia wei hts may be initially ad usted relative to one another to cause zero reading by said electric meter for unbalance of the revolving rotor in a selected transverse correction plane of the rotor and may be preliminarily calibrated by the employment of known weight means applied to the rotor to show the amount of unbalance in the rotor in another selected transverse correction plane of the rotor. j

2. The balance testing system presented in claim 1, in which the rotor in said machine is supplied with a graduated band around it, with a stroboscopic lamp cooperating with said band, an electric circuit to supply said lamp with electric current, and means to connect said lamp circuit with the piezoelectric crystal generator whereby to permitdetermination of the angular position of the unbalance of the rotor in said other selected transverse correction-plane of the rotor.

3. The balance testing system presented in claim 1, in which said support for said'weights on said pivot is a screw threaded rod with which screw threads on said weights permit adjustment of said weights along the rod.

4. The balance testing system set forth in claim 1, in which said weights are of different values, and in which said means supporting said weights on said pivot is a screw threaded rod with which screw threads on said weights cooperate line as the invention will retain all permitting said manual adjustment of the weights along such rod.

5. The balance testing system set forth in claim 1, in which the machine 'set forth in the claim revolves the rotor in a pair of aligned bearings, the generator pivot being mounted on one of said bearings.

6. The balance testing system set forth in claim 1, in which said meter is a vacuum-:type voltmeter.

'7. The balance testing system set forth in claim 1, in which said stroboscopic-lamp has a v control amplifier operatively associated with it.

8. The balance testing system presented in claim 1, in which only one of said two weights is adjustable toward and from the other companion weight.

9. Designed to coact with a machine of kno n type adapted to support and'to rotate on its axis a rotor to be tested with freedom for lateral, substantially horizontal vibration of the rotor due to its unbalance during such rotation. a balance testing system incorporating the comb nation of a pair of piezoelectric crystal gen rators each including a vertical axis pivot hav ng means operating its generator by turning of the i ot on its axis, each generator having means to mount its pivot on said machine in a manner to sub ect such pivot to said vibration of the rotat ng rotor. a longitudinal horizontal support fixed to each pivot and ex ending on o posite si es thereof and parallel to the geometrical axis of said rotor when such support is in its normal. neutral position, each such support having a pair of inertia Weights adjustably mounted individually on said su port on opposite sides of its pivot and each being manually adjustable longitudinally of its said support toward and from one another, each said generator having its electric circuit connected therewith, the two generators having at least one electric meter for use in said circuits to which the voltage created by said generator is conducted and by which it is indicated. whereby said inertia weight means may be initially adjusted relatively to one another in one generator to cause zero reading of the electric meter for unbalance of the revolving rotor in one selected transverse correction-plane of the latter and may be preliminarily calibrated by the employment of known weight means applied to the rotor to show the amount of unbalance in the rotor in a second selected transverse correction-plane of the rotor, and the weight means of the other generator may be initially adjusted relatively to one another to cause zero reading of the electric meter for unbalance of the revolving rotor in the second correctionplane of the latter and may be preliminarily calibrated by the employment of known weight means applied to the rotor to show the amount of unbalance in the rotor in the first correctionplane of the rotor.

10. The balance testing system set forth in claim 1 which incorporates two such piezoelectric crystal generators each having all of the properties and characteristics presented in such claim but cooperative nevertheless with the two different correction-planes of the rotor.

11. The balance testing system presented in claim 9, in which the rotor in the machine is supplied with a graduated band around it with a stroboscope-lamp cooperating with said band, an electric circuit to supply said lamp with electric current, and means to connect said lamp circuit individually with each of the piezo-electric crystal generators whereby to permit determination of the angular position oi the unbalance oi the rotor in each of the two selected transverse correction-planes oi the rotor.

12. The balance testing system set forth in claim 1 which incorporates two such piezoelectric crystal generators each having all of the properties and characteristics presented in such claim but cooperative nevetheless with the two difierent correction-planes of the rotor, the rotor having in said machine a graduated band around it, with a stroboscopic-lamp cooperating with said band, an electric circuit to supply said lamp with electric current, and means to connect said lamp circuit individually with each piezoelectric crystal generator whereby to permit determination of the angular position of the unbalance of the rotor in said two selected trans;

verse correction-planes of the rotor.

13. A balance tester, designed to coact with a balance testing machine of known type adapted to support and to rotate a rotor to be tested with freedom for lateral vibration in a predetermined plane due to imbalance in the rotating rotor, said tester including a pivot member, means to mount said pivot member on said testing machine to vibrate in agreement with the vibration of the geometric axis of the rotor in said predetermined plane, the axis 01' said pivot member being substantially at right angles to said predetermined plane of vibration of the rotor, inertia weight means, means mounting said inertia weight means on said pivot member upon opposite sides of the axis thereof, and with manual adjustment of at least one of said weight means toward and from said pivot axis, 'the longitudinal axis of said means for mounting said inertia weight means extending substantially parallel with the rotor axis in its neutral position, and indicating means actuated by the oscillation of said pivot member occasioned by said weight means'whereby said weight means may be preliminarily adjusted relative to one another to cause zero reading of said indicating means for unbalance in the rotating rotor in a selected transversecorrection plane of the latter, and may be preliminarily calibrated to show the amount of unbalance of the rotor in another selected transverse correction plane through the rotor.

14. The combination in a balance tester set forth in claim '13 in which said weight means is two weights of diflerent amounts.

15. The combination in abalance tester set forth in claim 13 in which said weight means is two weights, and in which said means mounting said weight means on said pivot member is a screw threaded rod permitting the specified adjustment.

16. The combination in a balance tester set forth in claim 13 in which said weight means is two weights of diil'erent values and in which said means mounting said weight means on said pivot member is a screw threaded rod permitting the manual adjustment of said two weights.

17. The combination in .a balance tester set forth in claim 13 in which said indicating means includes an electric current operated indicator and a circuit iorsaid indicator, and means for enerating impulses of current in said circuit, said means being responsive to oscillation of said pivot member. I

18. The combination in a balance tester set forth in claim 13 in which said indicating means includes an electric circuit containing a current operated indicator and a piezo-electric crystal enerator connected to and operat ng: i indisaid vibrational swing,

- 12 cator and actuated by the oscillation oi said pivot.

19. For usewith a balance testing machine adapted to rotate a rotor in a pair of bearings with freedom for horizontal lateral vibration due to unbalance in the rotating rotor, balance testing means comprising the combination of a pivot member, means to mount said pivot member on one of said bearings to vibrate in agreement with the transverse vibration of said bearings, the axis of said pivot member being substantially at right angles to the plane of vibration of said bearings. inertia weight means, means mounting said weight means on said pivot member on opposite sides of its axis and with manual adjustment of at least one 01 said weight means toward and from the axis of said pivot member, the longitudinal axis of said means for mounting said inertia weight means extending substantially parallel with the rotor axis in its neutral position, and indicating means controlled by the oscillation of said pivot member occasioned by said weight means, whereby said weight means may by preliminarily adjusted relative to said pivot member to cause zero reading of said indicating means for unbalance in the-rotating rotor in a selected transverse correction plane of the latter other than the transverse plane of the bearing on which said pivot member is mounted, and may be preliminarily calibrated to show the amount of unbalance of the rotor in another selected transverse correction plane of the rotor other than.

that of the bearing on which said pivot member is mounted.

20. The balance testing means set 'forth in claim 19 in which said inertia weightmeans is two weights of unequal values and in which said indicating means includes an electrically operated indicator specifying the status of said rotor, an electric circuit for said indicator, and an electric current impulse generating means in said circuit actuated by the oscillation of said pivot member.

21. In a machine of the class described, a support comprising bearings for a rotor to be tested permitting the axis of the rotor to swing vibrationally in a horizontal plane of vibration and to carry the bearings with it, an extension on one of said bearings, an inertia device mounted on said extension and comprising a pivot member having a vertical axis, a horizontal rod carried on said pivot member and having its longitudinal axis substantially parallel to the axis of the rotor in its neutral position, inertia weights of different masses carried on the rod on opposite sides of the pivot member, at least one of said weights being adjustable as to distance from the pivot member, and means sensitive to oscillation of said weights and rod about said pivot axis for indicating unbalance of the rotor.

22. In a device of the class described, a pair of bearings for rotatably supporting the ends of one of a number of rotors to be subjected to analysis, said bearings being supported to permit vibrational swing of the endsof the rotor in a single plane of vibration and to participate in a vibration detecting means associated with each bearing, each detecting means being connected with its associated bearing to participate in the vibrational swing of said bearing and comprising a pivot member disposed at right angles to the plane of vibration, a rod supported intermediate its ends on said pivot member, said rod being disposed with its longitudinal axis extending subeach of two transverse correction planes intersecting the rotor adjacent the corresponding bearings, indicating means for indicating the angular position of unbalanced forces in each of said correction planes, and an electric circuit and switches for connecting each of the electric pickups with each of said indicating means whereby the electric pickups govern the response of each of said indicating means.

23. In a machine of the class described for indicating the unbalance of a rotor by utilizing forces resulting from unbalance vibrations of the rotor during rotation, a support for an unbalanced rotor permitting vibratory motion thereof about a point, a vibration pick-up device mounted rigidly on said rotor support to receive said mib'ratory motion of "the rotor and comprising a frame secured to said rotor support, inertia-weight means, means carried by said frame and supporting said inertia-weight means for rotational oscillation upon a substantially fixed pivotal axis extending transverse to the direction of said vibratory motion, the mass of said inertia-weight means having some portion thereof on each side of said last named axis relative to the direction of force tending to vibrate the axis to provide an efiective moment arm for each portion of said inertia-weight means extending at an angle to a plane normal to the axis of the rotor, and means to adf'ust the corresponding effective moment of at least one of said portions to provide a difierential moment whereby a selected reference plane may be established for the rotor wherein unbalance 'in such plane does not oscillate the inertia-weight of on each side of the corresponding axis relative to the direction of force tending to vibrate the, axis to provide an effective moment arm for means and the latter is responsive only to rotor unbalance outside of said reference plane, resilient means coacting with said frame to bias said inertia-weight means to a predetermined normal position fixed relative to the direction of the effective vibratory force, and means responsive to the rotational oscillation of said inertia-weight means for indicating unbalance of the rotating rotor outside of said reference plane. w

24. In a machine of the class described f indicating the unbalance of a rotor by utilizing forces resulting from unbalance vibrations of the rotor during rotation, a pair of bearing members to support an unbalanced rotor for vibratory motion thereof about a point, a vibration pick-up device mounted rigidly on each said bearing member to receive said vibratory motion of the rotor and each comprising a frame secured to the corresponding bearing member, inertiaweight means, means carried by said frame and supporting said inertia-weight means for rotational oscillation upon a substantially fixed pivotal axis extending transverse to the direction of said vibratory motion, the mass of each said inertia-weight means having some portion thereeach portion of said inertia-weight means. ea:- tending at an angle to a plane normal to the axis of the rotor, resilient means coacting with the corresponding .frame to bias each said inertia-weight means to a predetermined normal position, means to adjust said inertia-weight means to vary the e fective moment thereof about the corresponding pivotal axis whereby each inertia-weight means is free from rotational oscillation resulting from unbalance forces lying in a different one of two predetermined reference planes normal to the rotor axis and responds to unbalance forces in said rotor external to said corresponding reference plane as related to a predetermined unbalance in the other of said reference planes, and means responsive to the rotational oscillation of each said inertia-weight means for indicating the amount of correction to be applied in the respective reference planes of the rotor and the location for such correction ctrcumferentially of the rotor.

25. The machine of claim 23 in which the unbalance indicating means is calibrated to indicate the apparent unbalance in a second reference plane which is the resultant of all unbalance outside said first reference plane for the rotor undergoing test.

26. The machine of claim 23 in which the inertia-weight means comprises two weight masses disposed on opposite sides of the pivotal axis therefor and adjustably spaced apart.

27. The machine of claim 23 in which the inertia-weight means comprises a threaded rod supported transversely of said fixed pivotal axis and at least one weight threaded upon each end of the rod for adjustment theron.

IRA A. WEAVER. CLYDE H. PHELPSQ References Cited in the tile of this patent UNITED STATES PATENTS Number Name Date 1,704,341 Rathbone Mar. 5, 1929 1,727,991 Kimball, Jr., et al. Sept. 10,1929 2,023,244 Schnaitter 1 Dec. 3, 1935' 2,050,073 'I'hearle Aug. 4, 1936 2,092,096 Swedlund -1. Sept. 7, 1937 2,131,602 Thearle Sept, 27, 1938 2,191,862 Sarazin Feb. 27, 1940 2,293,371 Van De Grii't Aug. 18, 1942 2,301,291 Kolesnik -1. Nov. 10, 1942 2,302,670 Buchanan Nov. 24, 1942 3,363,303 Ehrgott et al. Nov. 21, 1944 2,382,673 Sihvonen et al. .Aug. 14, 1945 2,382,843 'Annis Aug. 14, 1945 2,411,401 Welch Nov. 19, 1946 2,426,305 Hope Aug. 26, 1947' FOREIGN PATENTS Number Country Date Great Britain Oct. 18, 1937 

